You're one tough marine. You know it, and everyone that knows you knows it. Once stationed on Mars, you fought alone through the bloody cooridors of UACs science facilities and then into hell itself...just to stop an alien invasion.
Next you witnessed your home planet, Earth, be overrun by the demons you fought so bravely to destroy. They wrecked havoc, they took countless lives, and they really stank up the place. The remaining citizens of Earth took to the escape ships and got off the planet while you kept the demons busy. When all hope was thought to be lost, you found a way into the demon's lair, pushed them back, and killed the source of their invasion.
What then? Secretly, the UAC decides to move it's operation to Io, one of the moon's of Jupiter, thinking that this time they can successfully make teleportation technology work. Demon's come out of the gateway, but the UAC is ready and blasts them into oblivion. With UAC's eyes on the gateways they're experimenting with, the demon's come from behind in a spaceship teleported from their world and all inhabitants of the Jupiter moon are killed. Who was sent in to clean up the mess? Of course you remember, it was you.
Finally the Global Government had learned it's lesson. With UAC under new management, they now focused their technology on the Plutonia Experiment, creating a Quantum Accelerator which was used to close gates instead of open them. Just in time too, because an ancient demon had learned how to open its own gates on Earth at will. The Quantum Accelerator seemed to work at first, but when there were just too many gates to close, it failed and the demons overran once more. Before the demons could use the new technology of the Quantum Accelerator for their own purposes, you headed into the research facility that held it and put a stop to their schemes.
It seemed that this was finally the end of them.
Three years have passed since then. The remaining citizens of Earth have regrouped into one remaining city and have started to rebuild. You've been put on the city defenses and things seem to be going well...until one day. A startling explosion of sound and violence errupt from outside and your worst fears are proven true. Hordes of zombies and demons are roaming the streets and the familiar stench of death is in the air. How did this happen? Where did they come from this time? Looking in the distance, the city you were helping to rebuild is gone. It not that it's been destroyed, it just isn't there anymore. You recognize some of the buildings that stand before you, but the rest...? Come to think of it, you recognize them too. A pit forms in your stomach as you realize the only time you've seen them were when you waded through hell itself. How could both be in the same place? It's as if Earth and hell are fighting to share the same space. Too far from the supply depo to arm up, you pick up your pistol and head outside...
